1. Field of the Invention
The present invention relates to a driving circuit for a light emitting element.
2. Description of the Related Art
A light emitting diode (LED) is employed as a backlight for a liquid crystal panel, a light source configured as an incoming indicator for a cellular phone terminal, or otherwise an illumination device configured as an alternative to a fluorescent bulb. In order to control such an LED to emit light with a desired luminance, there is a need to configure a driving circuit to control a DC/DC converter so as to supply to the LED a sufficient driving voltage and a driving current that corresponds to the luminance.
Patent document 1 discloses a circuit configured to drive an LED with high efficiency. With such a technique disclosed in Patent document 1, an LED string and a constant current source are connected in series between an output terminal of a DC/DC converter and a fixed voltage terminal. With such an arrangement, the constant current source is configured as a variable current source which can adjust its current. Furthermore, the DC/DC converter is configured to control its output voltage such that a detection voltage Vdet which is a voltage drop that occurs at the constant current source matches a predetermined reference voltage Vref.